DNS SURVEYS

Open Resolvers

An ongoing survey that searches for open DNS resolvers.

Cache Poisoners

An ongoing survey that searches for DNS cache poisoners.

April 2005: Number of Nameservers

We probed 5% of routed IPv4 space, or 70 million addresses, looking for nameservers. For those that replied, we also tried to determine their software and version.

Zone and Nameserver Statistics

October 2009
October 2008
October 2007
August 2006
June 2005 With these surveys we send queries to 1,000,000+ zones and their authoritative nameservers looking for zones and nameservers that:
- Advertise their software version
- Allow recursion
- Allow zone transfers
- Exist on the same subnet
- Have delegations which differ from authoritative NS records
- Have lame delegations
- Have questionable SOA values
- Have mismatched serial numbers
- Utilize IPv6
- Utilize DNSSEC
- Publish SPF records
We also query a random 5% sample of routed IP addresses to look recursive resolvers and determine whether or not they openly provide service to anyone, and what software they are running.